1. Field of Invention
This invention relates to high temperature refractories and more particularly to a precast module or a plurality of precast modules of refractories for use as a leveling assembly in metallurgical vessels with sloping bottoms.
2. Brief Description
As will be recognized by those skilled in the art, in high temperature vessels such as molten steel ladles, one problem heretofore encountered relates to preventing slag from contaminating or otherwise being mixed with the relatively pure steel when it is being withdrawn from the vessel. Since slag is less dense than the molten steel, the slag tends to rise and accumulate on top of the underlying steel. If a pouring orifice is provided in the bottom of the vessel, relatively uncontaminated molten steel can be withdrawn simply by opening the orifice to permit the liquid steel to exit therethrough. However, when the liquid surface falls until it is near the bottom of the vessel, pouring must stop before slag exits along with the remaining steel; and thus a quantity of steel remains in the vessel and is unusable. In order to keep this unusable quantity as small as practicable, it has become customary to provide sloping bottoms with a low point at or near the edge of the vessel where a pouring orifice is positioned. However, this has brought about a relative inefficiency in refractory brick installation and utilization.
The harsh and erosive properties of slag are well known; and in order to protect walls of a vessel in the vicinity of slag locations, a refractory brick that is more slag-resistant (and more expensive) than refractory bricks for contact with molten steel has been required. Thus, less expensive refractory bricks that are acceptable for use in contact with molten steel do not adequately withstand the rigors of on-going contact with slag. Accordingly, it has been customary to line the interior of a metallurgical vessel designed for use with molten steel (e.g., a ladle) with lesser cost refractory bricks in regions normally encountering mostly liquid steel, while installing the more costly bricks in regions expected to normally encounter slag. Since slag normally resides on the surface of the molten steel, such more costly bricks are used to line the upper region of the interior which usually is adjacent the mouth of the vessel.
For simplicity and cost effectiveness, it is customary to line the interior of a high temperature vessel with refractory bricks beginning at the bottom; and, after installing bricks overlying the bottom, to work upward to cover the interior walls with successive courses until the entire interior has been covered. It will thus be observed that if the bottom slopes, the successive rings of side wall bricks will also slope, forming rings that are tilted to follow the slope of the bottom. However, the surface of the liquid contents of the vessel will be horizontal, generally parallel to the plane containing the earth's natural surface at that location; and so the plane containing the liquid surface will lie at an angle to the planes of the successive rings of refractories. Accordingly, in order to ensure that normal contact between slag and refractories is in a region of the lining in which the more expensive bricks are installed, it has been necessary to provide several full or partial extra courses of such more expensive bricks.
Recognizing that sloped bottoms can increase the yield of metal recovered, it has been desired to modify essentially flat bottomed vessels to give them an effective sloped bottom to obtain larger recovery of uncontaminated metal.
Heretofore, the use of refractory castables or ramming mixes to compensate for the slope was generally unsatisfactory since cast or rammed fillers require extended, and hence costly, installation time.